1. Field of the Invention
The present invention relates to vehicle roll-over bars, and particularly adjustable height vehicle roll-over bars for use in connection with work vehicles such as agricultural tractors.
2. Description of the Related Art
With the exception of very small, relatively lightweight vehicles such as lawn and garden tractors, most vehicles are provided with some form of roll-over protection system, or ROPS, to prevent the vehicle from crushing the operator if it accidentally rolls over. The simplest such ROPS widely used on small agricultural tractors is a U-shaped bar. The ends of the U are attached to the frame of the tractor and the base of the U is positioned in the vicinity of the vehicIe's operator station. The sides of the U may be perfectly vertical, but typically are sloped slightly back from the operator station to provide additional clearance around the operator station.
Different vehicle configurations may require different roll-over bars. The roll-over bar must, of course, be taller than even the tallest person likely to be operating the vehicle. At the same time, however, it is preferable to have the roll-over bar as short as possible within this limitation to maximize overhead clearance of the vehicle.
The addition of certain implements to the vehicle may have an impact on the preferred height of the ROPS. For example, a John Deere model 750 utility tractor, shown in FIG. 1 at 10, comes equipped with a U-shaped roll-over bar 12. This roll-over bar 12 has a height selected to provide adequate protection for the operator station 13 while at the same time being short enough to maximize the overhead clearance of the vehicle. However, such a tractor can be equipped with a backhoe, shown in phantom lines at 14. This backhoe is provided with a separate seat 16, shown in the drawing in its inactive position, which when moved down into its active position is positioned somewhat above the normal seat for the tractor 10. As a result, the normal roll-over bar 12 is too short to provide adequate space when the operator is seated in seat 16, and a taller roll-over bar 18 must be substituted therefor.
In the past, this substitution has been accomplished by simply maintaining two stocks of roll-over bars, the shorter version for use on most tractors and the taller version for use on the smaller number of tractors to be equipped with backhoes. The dealer making the ultimate sale normally will substitute the taller ROPS for the shorter ROPS when appropriate.
This technique has several disadvantages. First, the dealer must maintain a supply of both size ROPS. This ties up both capital and storage space. Second, the attachment points for the U-ends of the ROPS sometimes are not easily accessible, so that substituting a different ROPS can be time-consuming.